In a survey of office workers just released by CareerBuilder, 39 percent say they have dated a co-worker at least once in their career. Of the ones who dated, 29 percent dated a higher-up; 16 percent dated their boss. Most workers said they had been open about these relationships, but 35 percent kept them secret.

Clarence Belnavis, a partner in the Portland, Ore., office of Fisher & Phillips, counsels clients on the dangers of office romance. It's no secret, he says, says why love is blooming in the office: It's where people spend most of their time, he tells ABC News. "You spend more time at work than you do sleeping. No wonder a good number of people find their significant others there."

Even so, he says, most employers don't know how to deal—or don't want to deal—with the legal issues raised by these relationships. "Very few deal with it in a pro-active fashion," he says.

There's nothing illegal about love in the office, provided it's consensual and not the result of intimidation or coercion.

Nor is it illegal for a lover to show favoritism at work toward his beloved. "Paramour favoritism" is the legal term for that, says Belnavis, and courts have found it to be neither harassment nor gender discrimination, for purposes of the Civil Rights Act.

The reason, says Belnavis, is that the favoritism shown to the paramour disadvantages all other employees equally, whether they are male or female. Further, according to The Legal Intelligencer, paramour favoritism does not run afoul of Equal Employment Opportunity Commission guidelines, which permit isolated instances of preferential treatment based on consensual romantic relationships.

Favoritism shown a paramour may be unfair to other workers, the commission has ruled, but the unfairness is based on considerations other than the gender of the disadvantaged parties.

What makes consensual office love relationships problematic for employers, Belnavis says, is that consent can be withdrawn at any time.

"Today's consensual relationship," he says, "can be tomorrow's breakup disaster." Suddenly, one party's attentions are no longer welcome to the other. Put another way: "High school is alive and well in the workplace."

Despite the danger that the jilted lover will sue, alleging, say, that the relationship was coercive and that the employer allowed it to exist, Belnavis says most employers choose not to intervene in office romances. "They feel it's taboo for them to interfere in that aspect of employees' lives."

Michael Woolley, associate general counsel for trucking company C.R. England in Salt Lake City, Utah, tells the Wall St. Journal his company does not ban in-office relationships. But when and if management learns of that two employees are pitching woo, it calls a meeting with them, to discuss the situation.

In rare instances, says Woolley, the company will draft a so-called "love contract" stipulating that the relationship is consensual, and setting ground rules for the couple's behavior in the workplace. One reason love contracts are rare, he says, is that the necessary negotiations can make for awkward conversations between manager and employees.

Belnavis says he has been recommending love contracts to his clients since 2001.

He calls them useful tools for establishing the ground rules and boundaries for an office romance. If love goes sour and charges of harassment start to fly, they offer some measure of protection for management, who can cite them as proof that the relationship was consensual and that management sat the couple down and explained what standard of behavior was expected of them.

A well-drafted love contract, says Belnavis, might include some or all of the following elements: acknowledgement by the parties that a relationship exists; that it is not based on intimidation; that the employees understand the company's policies on sexual harassment and discrimination; and that they commit to keeping management informed of any changes in their relationship. It might also include a commitment not to engage in retaliation, should the romance end.

"Love contract" is a bit of a misnomer, says Belnavis, noting that nothing is bought or sold. "It's more what I would call a relationship-acknowledgement form."

He emphasizes that the document, while useful, is not a cure for relationships that are wrong by definition—a romance between a manager and an immediate subordinate, say.

How should office lovebirds who are peers comport themselves, to avoid trouble?

Rachel DeAlto, a self-described flirting and communications expert, is author of "Flirt Fearlessly," an A to Z guide to fraternization. Her list of do's and don'ts for office sweethearts, published in The Advertiser of Lake City, Fla., includes the following:

Find out what policy, if any, your office has about workplace romance: If your company forbids it, don't do it. Or, alternatively, resign: If you've found the love of your life, keep your paramour and find a job somewhere else.

If company policy permits romance but requires that you notify HR of your relationship, report it at its earliest stage.

Respect decorum: If romance is permitted, have the good taste not to rub yours in co-workers' faces. "Making out at the Christmas party or causing your colleagues to feel uncomfortable with your public displays of affection," advises DeAlto, "is never cute. Keep all outward shows of affection for outside the office."

Likewise, keep all love-problems at home. Don't allow them to taint your professional life or those of co-workers.